The objective of the proposed research is to understand, in chemical terms, the biological activities of three erythrocyte hemeproteins- cytochrome b5, cyanide-binding hemeprotein, and hemeprotein 559, an erythrocyte pink copper protein and a naturally occurring copper-gamma-globulin complex. Homogeneous proteins from human and bovine erythrocytes will be subjected to chemical, physical, immunological, and catalytic studies. The primary structure, physical properties, and catalytic properties of erythrocyte cytochrome b5 will be determined and compared to liver microsomal cytochrome b5. The role of cytochrome b5 in the reduction of methemoglobin will be further studied. We will attempt to establish the structure of the unique prosthetic group of the cyanide-binding hemeprotein by mass spectral studies of derivatives of the heme. Oxidase activities of this protein will be surveyed. An attempt will be made to assign the biological function of the cyanide-binding protein and to detect this protein in other cells. The chemical, physical, and immunological properties of hemeprotein 559 will be studied in order to establish whether this protein is a degraded form of cytochrome P-450. The pink copper protein of erythrocytes will be studied to determine the nature of its chromophore and to characterize and understand the significance of its oxidase activity. The copper-gamma-globulin complex will be degraded in an effort to identify the structural features responsible for the tight binding of copper. The results of these studies are important in terms of understanding the chemistry of the unique prosthetic groups, the mechanism of catalysis, and the metabolism of erythrocytes. Furthermore, these studies may provide a better understanding of red blood cell maturation and aging, and the problems of blood storage, copper deficiency, copper toxicity, multiple myeloma, methemoglobinemia and erythroleukemia. BIBLIOGRAPHIC REFERENCES: Hultquist, D.E., Douglas, R.H. and Dean, R.T. (1975) The Methemoglobin Reduction System of Erythrocytes, Proceedings of the Third International Conference on Red cell Metabolism and Function (G. Brewer, ed.) 297. DeFilippi, L.J. and Hultquist, D.E. (1975) A Micro-Scale Isolation of Hemins from Hemeproteins Using Polyacrylamide Gel Electrophoresis, Arch. Biochem. Biophys. 170, 670.